It is shown that statistical process models for the mixing process in the internal mixer, which are based on characteristical variables, are essentially suitable for on-line calculation of compound properties of relevance for quality. In order to identify the influences of individual process parameters and any disturbance variables that may prevail on specific quality characteristics, ii is, however; first process analyses. By using characteristic variables calculated from recorded process curves, it is possible to record process. The current stage of the research into the modelling of the mixing process in an internal mixer with the aid ed with examples for a natural rubber and an SBR compound.